Mechanisms underlying the control of gene expression are of central importance in understanding growth and development in all organisms. Gene expression is controlled at transcriptional and posttranscriptional levels. Understanding transcription regulatory mechanisms in eukayrotes is the long range objective of the research proposed here, and specific objectives are (a) to determine what specific transcription factors interact with eukaryotic nuclear RNA polymerases to facilitate accurate transcription as well as modulate transcription (b) to determine the evolutionary conservation of these processes in eukaryotes, and (c) to determine the functional roles played by RNA polymerase subunits in the transcription process. Major emphasis will be placed on determining which transcription factors can replace analogous transcription factors in transcription systems from different species and which transcription factors are species-specific. RNA polymerases appear to show species- specificity especially in regard to some of their smaller subunits and possibly a carboxyl terminal domain in the largest subunit of RNA polymerase II. It is likely that the species-specificity displayed by RNA polymerases has a counterpart in species-specific transcription factors that interact directly or indirectly with the RNA polymerases. This hypothesis will be tested by attempting to complement a transcription system form human cells with transcription factors purified from a distantly related species (i.e., plants). In addition, the interaction of RNA polymerases with specific transcription factors from divergent species will be tested using RNA polymerase affinity chromatography and RNA polymerase binding assays. As a first step in determining the putative roles played by some of the small RNA polymerase subunits, genes will be isolated and sequenced. This approach has provided a wealth of information on the large subunits of RNA domains, nucleotide binding domains) to the largest subunits of Prokaryotic RNA polymerase. In addition, the isolation of these genes will provide specific probes for studying the regulation of RNA polymerase gene expression.